Tobit model specification

[Marine Jouvin]

Hi,

I plan on using a Tobit model as my dependent variable is the number of transactions reported on an application. I thus have exclusively positive values, but around 25% of 0 (for the ones who didn't use the app at all).

I was wondering which of the following specifications should use :

    tobit y x

    tobit y x, ll(0)

Whether or not to use ll(0) is unclear to me. The help related to the Tobit command in Stata states that "You do not have to specify the censoring value.", but the regression results differ depending on whether or not ll(0) is added.

[Andrew Musau]

Without specifying a censoring limit, you are just estimating a linear regression model, i.e.,

tobit y x

is equivalent to

regress y x